HP 8200zl / VLAN routing and SNMP

Hello,

I currently cannot find any way to graph the amount of traffic that the switch is routing for a VLAN. The VLAN interfaces in the interface MIB table stay at 0 because it seems it only covers the case where the switch receive data for himself (so not routing).

I checked the result of the command "sh ip counters vlan X ipv4", but the values are far too low to be the routing counters.